Transition metal atoms embedded graphyne as effective catalysts for nitrate electroreduction to ammonia: A theoretical study

Electrocatalytic nitrate reduction reaction (NO₃RR) to ammonia has been proved to be a viable approach to dispose of nitrates pollution and simultaneously fabricate valuable ammonia at room temperature and pressure. It is essential to explore high-performance and selective electrocatalysts for NO₃RR to overcome the sluggish kinetics. Herein, through adopting a four-step screening route based upon the calculation of density functional theory (DFT), we have performed a comprehensive investigation on the NO₃RR catalytic activities for single-atom catalysts (SACs), taking transition metal atom embedded graphyne (TM-GY, TM = 3d ∼ 5d) as example. The computation results show that the electrochemical conversion of nitrate-to-ammonia can be realized on Cr-GY candidate with an extremely low limiting potential (−0.36 V) and high selectivity, which can be ascribed to the moderate adsorption strength between the intermediate species and Cr atom derived from its distinct electronic property. Our study not only reveals the NO₃RR catalytic origin of TM-GY, but also provides a new route for the rational design of electrocatalysts for nitrate reduction to ammonia.